Biochemical characterization and autoradiographic localization of [3H]PGE2 binding sites in rat kidney

Specific binding sites for prostaglandin E2 (PGE2) in membranes obtained from whole kidney and from different areas of rat renal tissue were identified and quantified by in-vitro radioligand binding and localized by autoradiography. Analysis of the [3H]PGE2 binding by Scatchard plots revealed a single class of high-affinity binding sites in the whole kidney (KD = 5.1 +/- 0.4 nM; Bmax = 75 +/- 9 fmol mg-1 protein), the cortex (KD = 6.1 +/- 0.5 nM; Bmax = 58 +/- 5 fmol mg-1 protein) and the outer medulla (KD = 3.3 +/- 0.3 nM; Bmax = 376 +/- 59 fmol mg-1 protein). No reproducible Scatchard plots could be obtained in the inner medulla. PGE1 was equipotent with PGE2 in inhibiting [3H]PGE2 binding, whereas PGA2, PGB2, PGF2 alpha and PGI2 were 10- to 1000-fold less potent. Autoradiographs revealed sparse or no binding in glomeruli, proximal tubules or blood vessels. The pattern of distribution of [3H]PGE2 binding was consistent with the anatomical localization of the distal tubule and in particular the thick ascending limbs of Henle. Based on the distribution and cellular localization of the [3H]PGE2 binding sites, our data support the hypothesis that the physiological role of PGE2 receptors is coupled to the regulation of sodium transport across segments of the distal tubule.